Unlike Tor, mix networks do not require many mixes to serve a great many clients because mix networks do not require route unpredictability for the anonymity properties. Therefore the inclination may be to create mix networks with a very small number of mixes such as 6 mixes or so. The problem with this setup is that it's relatively cheap to compromise a mere 6 machines as compared to Tor where there are thousands of relays. Therefore we should regard mix networks with a small number of mixes as vulnerable to compromise.
We should investigate the cost of compromise of a large percentage of mixes versus mix network capacity. Obviously if a mix network has too many mixes as compared to mix traffic this would be very bad in the case of the poisson mix strategy; it would mean that each mix would receive too little traffic to have a large enough anonymity set size (entropy).
Unlike Tor, mix networks do not require many mixes to serve a great many clients because mix networks do not require route unpredictability for the anonymity properties. Therefore the inclination may be to create mix networks with a very small number of mixes such as 6 mixes or so. The problem with this setup is that it's relatively cheap to compromise a mere 6 machines as compared to Tor where there are thousands of relays. Therefore we should regard mix networks with a small number of mixes as vulnerable to compromise.
We should investigate the cost of compromise of a large percentage of mixes versus mix network capacity. Obviously if a mix network has too many mixes as compared to mix traffic this would be very bad in the case of the poisson mix strategy; it would mean that each mix would receive too little traffic to have a large enough anonymity set size (entropy).